An optical coherence tomography (OCT, hereafter) is used for forming images representing a surface morphology and an internal morphology of an object to be measured. An artifact due to a reflection from an object other than the object to be measured or a phenomenon of coherence revival may appear in an OCT image acquired by using OCT. Their artifacts may appear overlapping with the attention site or affect results of image processing such as a segmentation processing, or the like.
For example, an artifact due to a reflection from the object other than the object to be measured may be removed by applying an anti-reflection coating to an optical member constituting an interference optical system for acquiring the OCT image. Also, a method to remove an artifact by performing phase modulation with respect to light from a light source so as to suppress occurrence of the phenomenon of coherence revival is known (US Unexamined Patent Application Publication No. 2014/0029015).
However, even if the anti-reflection coating is applied to the optical member, it is difficult to suppress the reflection perfectly. In addition, in the method disclosed in US Unexamined Patent Application Publication No. 2014/0029015, design depending on an optical condition such as kinds or placement of the optical member constituting the optical system is needed, and thereby this makes it complicated to design the optical system and a control system.
In general, artifacts due to the reflection from the object other than the object to be measured are more likely to appear in the OCT image as coherence length becomes longer. Furthermore, artifacts due to the phenomenon of coherence revival are more likely to appear in the OCT image as interval of coherence revival becomes shorter. Therefore, in case of using a light source of which coherence length is long or a light source of which interval of coherence revival is short, deterioration of the OCT image is more likely to occur, and thereby a new technology is required to remove the artifact described above.